I certainly do not know why I persevered but at the time I was learning the art of digital photography and found Alamy to be a very good teacher, along with lots of very obliging contributors at that time giving advice too through the forums.
As far as income, well, it leaves a lot to be desired but a lot of that is down to me and the type of images I produce and the keywording I apply to my images.
Yes it is a hobby and gives me an interest, among other things, in my retirement even if it does not supplement my pension income.
I have also been lucky in meeting some very nice people through the Cambridge contributor group meetings who have become good friends.
Yes I think it has been worth it and pleased I persevered after all.